Rear Guards on Tractor-Trailers Pose Fatal Danger

New crash tests and analysis conducted by the Insurance Institute for Highway Safety reveal that tractor-trailers underride guards can fail in even low-speed crashes and can lead to fatalities. The Institute is petitioning the federal government to mandate stronger underride guards, constructed to stay in place during a crash and is also asking that guards be in place for large trucks and trailers.

Rear guards are meant to minimize underride injuries and fatalities in crashes in which a passenger vehicle hits the rear of a tractor-trailer. In 2009, said the Institute, 70 percent of the 3,163 people who died in large truck crashes were passengers in cars or other passenger vehicles.

Underride increases the likelihood of a fatality or significant injury in these types of accidents because, typically, the upper portion of a passenger vehicle’s passenger area is the part of the vehicle that will generally crush upon impact with of the truck body into the vehicleâ€™s safety cage, said the Institute.

“Cars’ front-end structures are designed to manage a tremendous amount of crash energy in a way that minimizes injuries for their occupants,” Adrian Lund, Institute president, said in a statement announcing the findings of its tests. “Hitting the back of a large truck is a game changer.” The Institute statement pointed out that a person could be driving in a vehicle that earned high ratings in frontal crash tests, but when a truck is not equipped with an underride guard or that guard fails, the chances of walking away unharmed or alive from even a low-speed crash, are minimal.

The Insurance Institute for Highway Safety has been studying underride crash issues for 30 years, such as crash tests from the 1970s that revealed how guards in use then did not prevent underride. The newest Institute analysis reviewed case files from the Large Truck Crash Causation Study, a federal database of about 1,000 real-world crashes from 2001 to 2003. The Institute identified crash patterns that led to rear underride of heavy trucks and semi-trailers that were and were not outfitted with guards. In most of the 115 crashes, underride occurred when a passenger vehicle hit the back of a heavy truck or semi-trailer; 22 percent did not involve underride or suffered negligible underride. In 23 of the 28 passenger vehicle fatalities, there was what the Institute described as severe or catastrophic underride damage: The entire front end or more of the vehicle slid under the truck.

The National Highway Traffic Safety Administration (NHTSA) estimates that 423 people in passenger vehicles die annually in accidents in which their vehicles hit the backs of large trucks; over 5,000 passenger vehicle occupants are hurt.

The Institute conducted crash tests with three semi-trailer rear guards in compliance with U.S. rules; two are also certified under stricter Canadian mandates for strength and energy absorption. A 2010 Chevrolet Malibuâ€”a mid-size sedan that is the Instituteâ€™s top safety pick and a five-star-rated NHTSA car in its New Car Assessment programâ€”was used, not tested, to strike the rear of parked trailers.

Decapitation is one of the significant underride threats with the Institute finding that in three of the crash tests, the crash test dummy heads made contact with either the trailer or the carâ€™s hood after it tore free and pushed into the occupant compartment.

The Institute also ran tests to determine outcomes when a car hits the trailer with only part of its front instead of head-on. Even the strongest guard left about half of the rear of the trailer vulnerable to severe underride and only worked as intended when the car struck the trailerâ€™s center.

Many heavy trucks to go without guards due to regulatory gaps and even exempt trucks are not incompliance with 1996 strength and energy absorption regulations, said the Institute. “Underride standards haven’t kept pace with improvements in passenger vehicle crashworthiness,” Lund said in the group’s statement. “Absent regulation, there’s little incentive for manufacturers to improve underride countermeasures, so we hope NHTSA will move quickly on our petition.”